engleski

Interaction of polysaccharides with lipid monolayers

The interactions of model neutral lipids such as lecithin and dipalmitoyl phosphatidylcholine (DPPC), and of the positively charged lipid dioctadecyl dimethyl ammonium bromide (DOMA) with neutral (dextrans) and acidic polysaccharides (carrageenans and xanthan), representing the hydrophilic solutes occurring in natural aquatic systems, have been monitored electrochemically and by monolayer techniques. Surface pressure-area (p -A) and surface potential-area (D V-A) isotherms have been measured. The values for compressibility of mixed films and the dipol moments (effective dipole moment m T and polar head group dipole moment m a ) have been calculated from p -A and D V-A isotherms, respectively. In electrochemical experiments lipid coated mercury electrodes have been used. The influence of polysaccharides on the monolayers structure have been studied by capacitance measurements and by using electrochemical probe (redox processes of cadmium) with phase sensitive a.c.voltammetry. The results presented here are part of more general studies of the interaction of organic solutes naturally occurring in the aquatic systems with hydrophobic lipids at different phase boundaries. These investigations are of great importance regarding the interfacial properties of mixed monolayers and to understand the influence of hydrophilic and hydrophobic substances on the physico-chemical properties of natural surface films.

Polysaccharides; Lipid monolayers; Air/water interface; Capacity measurements; ac voltammetry

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